Submerged direct contact vaporization process

ABSTRACT

Vaporizing a liquefied gas by feeding the hot products of combustion of a combustible material into and below the surface of a mass of the liquefied gas in a tank, said liquefied gas being at a temperature at which at least water in the hot products of combustion is solidified, removing from the tank unsolidified products of combustion in admixture with the vaporized gas formed by heat exchange between the hot products of combustion and the liquefied gas and at least periodically removing from the tank solidified water.

United States Patent 1 1 Larsen 1 1 Oct. 2, 1973 1 1 SUBMERGED DIRECTCONTACT VAPORIZATION PROCESS [75 I Inventor: Lyle Vernon Larsen,Naperville,

lll.

[ 73 Assignee: Chicago Bridge & Iron Company, Oak Brook, 111.

[221 Filed: Apr. 19, 1971 211 Appl. No.: 135,197

[52] US. Cl 48/190, 48/196 R, 62/52, 261/77, 261/123 [51] Int. Cl Fl7c7/02, Fl7d 1/04 [58] Field of Search 48/190,196 R, 196 VS; 62/52 US, 50US; 23/281 [56] References Cited UNITED STATES PATENTS 3,431,743 3/1969Green ..62/52 2,463,098 3/1949 Goddard 48/61 3,413,810 12/1968 Kaufmann.50/261 X 3,524,319 8/1970 Stockel 60/261 UX 2,921,004 1/1960 Wood126/350 X 3,107,482 10/1963 FOnO 60/39.]6 R 3,088,812 5/1963 Bitterlichet all. 23/281 FOREIGN PATENTS OR APPLICATIONS 1,158,934 7/1969 GreatBritain 48/190 Primary Examiner-Joseph Scovronek AttorneyMerriam,Marshall, Shapiro & Klose 57 ABSTRACT Vaporizing a liquefied gas byfeeding the hot products of combustion of a combustible material intoand below the surface of a mass of the liquefied gas in a tank, saidliquefied gas being at a temperature at which at least water in the hotproducts of combustion is solidified, removing from the tankunsolidified products of combustion in admixture with the vaporized gasformed by heat exchange between the hot products of combustion and theliquefied gas and at least periodically removing from the tanksolidified water.

7 Claims, 1 Drawing Figure PATENTED V 2'975 3. 752.893

4 3/? 797/7102: [amen SUBMERGED DIRECT CONTACT VAPORIZATION PROCESS Thisinvention relates to apparatus and methods for gasifying or vaporizingliquids. More particularly, this invention is concerned with apparatusand processes for gasifying or vaporizing liquefied gases.

Although many products are stored and transported as liquids, it isoften necessary for the liquids to be gasified or vaporized for varioususes. This is particularly so for materials which are normally gases atambient temperatures and pressures but which have been converted toliquids for storage and other handling purposes. Among the liquefiedgases which are normally vaporized for subsequent use are liquefiednatural gas, liquefied petroleum gas, methane, ethane, propane andnitrogen.

The vaporization of liquefied gases is normally effected by indirectheat exchange, such as by the use of conventional shelland-tube heatexchangers. This approach generally requires a large capital investmentfor equipment where the volume of gas or vapor to be produced is large.There is accordingly a need for improved apparatus and methods forgasifying liquefied gases and particularly liquefied gases which arecombustible.

According to the present invention, there is provided a method ofgasifying or vaporizing a liquefied gas which comprises feeding the hotproducts of combustion of a combustible material into and belowthesurface of a mass of a liquefied gas product in a vessel, saidliquefied gas being at a temperature at which at least water in the hotproducts of combustion is solidified, removing from the vesselunsolidified products of combustion in admixture with the vaporized gasproduct formed by direct heat exchange between the hot products ofcombustion and the liquefied gas product, and at least periodicallyremoving from the vessel water and other materials, both solidified andunsolidified.

Also provided by the invention is suitable apparatus which can be usedin practicing the described process as well as modifications thereof.

The invention will now be described further in con junction with theattachedgdrawing in which there is shown in schematic form apparatus foruse in practicing the invention.

With reference to the drawing, vessel has a top semispherical shellportion 11 which is joined to a central cylindrical shell portion 12which is broken away since it can be higher than convenientlyillustrated. A bottom conical shell portion 13 is joined to shellportion 12 and completes the vessel structure. The top shell portion 11of vessel 10 has a vertical cylindrical tubular shell portion 14 whichis in communication with the inside of vessel 10. Extending outwardlyfrom the upper part of tubular portion 14 is pipe or conduit 15. The topof tubular shell portion 14 is capped by cover 16.

The major elements of burner are located inside of tubular shell portion14 and vessel 10. Burner 20 has a fuel supply pipe 21 in communicationwith the upper reduced enclosed end portion 22 of the burner. Wires 23are located in the portion 22 to supply electric power to a spark device24 for the purpose of igniting a combustible mixture supplied thereto bypipe 21. Combustion chamber 25 is defined by elongated tube or pipe 26which has its lower end or mouth 27 located to be below the designatedliquid level of liquefied gas to be held by vessel 10 for vaporization.Insulation 33 is advisably placed around the outside surface of theportion of tube 26 which extends into the liquefied gas. The insulationserves to keep the combustion products hotter as they leave mouth 27 ofthe tube and to thereby supply more heat to the liquefied gas. Tube 26has a tapered upper section 32 which communicates with end portion 22 ofthe burner. A vertically positioned cylindrical baffle 28 is located invessel 10 in spaced away arrangement from pipe 26. The bottom and top ofcylindrical baffle 28 are open so that liquefied gas in vessel 10 canflow in and out thereof.

Conduit 29 communicates with the interior of vessel 10 to supply aliquefied gas to be vaporized into the vessel. insulation 30 isadvisably positioned around vessel 10 although for some purposes suchinsulation may be unnecessary.

In practicing the process of this invention, a liquefied gas is suppliedby conduit 29 to vessel 10. Sufficient liquefied gas is filled intovessel 10 to advisably bring it to a liquid levelabove the lower end 27of the combustion tube 26 so that the hot combustion products bubblethrough the liquefied gas before they reach the liquid surface. Acombustible mixture is supplied by conduit 21 through the reducedtubular part 22 of the burner into the combustion chamber 25 of tube 26.An ignition spark is provided by igniter 24 to cause the combustiblemixture to burn. The hot products of combustion of the combustiblematerial: stream downwardly through combustion chamber 25 and areexpelled at the lower end or mouth 27 thereof. The hot combustionproducts thereafter flow upwardly in the liquefied gas between the outersurface of the lower end 27 of tube 26 and the inner surface ofcylindrical baffle 28. As the hot products of combustion flow throughthe liquefied gas, heat transfer results and this leads to vaporizationofsome of the liquefied gas. The resulting admixture of vapors, formedby vaporization of the liquefied gas, and the products of combustionwhich do not solidify in the liquefied gas, flows upwardly in the space31 surrounding burner tube 26 in the cylindrical portion 14. Thisresults in heat exchange between hot products of combustion inside oftube 26 and the gas vapor and products of combustion on the outsidethereof. The resulting admixture is then conveyed to pipe 15 which canfeed it to any suitable destination such as a consumer line or otherconduit for use in a manufacturing process.

By burning a combustible material in combustion chamber 25, someproducts are formed which are undesirable in the subsequently formedadmixture of vaporized liquefied gas and products of combustion. Chiefamongst these undesirable materials is an excess of water vapor. Theamount of water and other materials however is readily reduced, andsometimes substantially eliminated, by the process of this invention bysolidification through contact with the liquefied gas in vessel 10. Theliquefied gas is generally at a temperature substantially below thefreezing point of water so that as a result water vapor is quite readilysolidified through contact and heat transfer with the liquefied gas.

It is desirable sometimes simply to reduce the amount of water vapor andother solidified products in the resulting admixture rather than tosubstantially eliminate these materials. By regulating the depth atwhich the mouth 27 of tube 26 is placed in the liquefied gas and byproper spacing of cylindrical baffle 28, the residence time of productsof combustion can be adjusted to control the amounts of water vapor orother products in the admixture of combustion gases and vaporizedliquefied gas.

While the use of baffle 28 is advisable it is not considered essentialto practice the invention.

Any suitable combustible mixture can be supplied by means of conduit 21.The fuel can be a hydrocarbon liquid such as fuel oil, kerosene orgasoline, or a gas such as natural gas, ethane, petroleum gas orpropane. In addition, the oxidizing agent can be air, enriched air oressentially pure oxygen. it is generally preferred to use as thecombustible mixture a previously prepared mixture of natural gas andair. Such a mixture is especially useful if the liquefied gas to bevaporized is liquefied natural gas.

Products which solidify in the liquefied gas in vessel settle to thebottom of the vessel. The ice particles and other particles accumulatein the lower central part of the conical bottom shell portion 13 ofvessel 10. These solidified materials can be removed periodically orcontinuously from vessel 10 by opening valve 35 and permitting thesolids, together with some of the liquefied gas, to flow out by means ofconduit 36. The drained material can be disposed of in any mannerconsidered suitable. Advisably, the material is sent to a second vessel40.

Vessel 40 is advisably noninsulated and this permits a ready heatexchange with the atmosphere and leads to melting of the ice in vessel40 and the vaporization therein of solidified carbon dioxide andwhatever liquefied gas is also fed thereto in conjunction with the solidmaterials. Vessel 40 can also be heated by means of a secondary sourceof heat, if desired, to accelerate melting of solids therein. The watercan be removed by conduit 41 which communicates with the lower internalpart of vessel 40. To drain the water, valve 42 is opened and the wateris conveyed from the valve by conduit 43 to a suitable disposal means.Vapor which forms in vessel 40 may be removed therefrom by conduit 44,which communicates with the internal upper space of tank 40,

through valve 45, when open, and fed into conduit 46 for admixture withvapors from conduit 15. This may be desirable to control the heat valueof a combustible gas which has been formed by vaporization of the gas inliquid form. Quite often a liquefied combustible gas after vaporizationwill have a considerably higher heat value than is either desired orrequired for an intended purpose and it accordingly is necessary toreduce its heating value through dilution of the vapor with a gas whichsupplies no heating value. Alternatively, vapor can be fed by conduit 44to conduit 47, through valve 48 and out conduit 49 to be used asconsidered advisable or wasted. Of course, when this is done valve 45 isclosed.

A portion or all of the vaporized gas and combustion gases canalternatively be removed from vessel 10 by means of conduit 50 insteadof circulating all or part of the vapors around the burner and removingthem by conduit 15.

To remove the undesirable materials from the combustion products bysolidifying them in the liquefied gas, the liquefied gas in vessel 10should advisably be below 32F. In the case ofliquefied natural gas, theliquefied gas can be obtained from a storage tank in which it is quitecommonly stored at about 260F. and 15 psia for use in the describedprocess. Also, liquefied petroleum gases, which are often stored ataround 55F., are clearly cold enough for use in the described process.

The foregoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, as modifications will be obvious to those skilled in the art.

What is claimed is: l. The method of vaporizing a liquefied gas whichcomprises:

feeding the hot products of combustion of a combustible material intoand below the surface of a mass of a liquefied gas in a vessel, saidliquefied gas being at a temperature at which at least water in the hotproducts of combustion is solidified;

removing from the vessel unsolidified products of combustion inadmixture with vaporized gas product formed by heat exchange between thehot products of combustion and the liquefied gas; and

at least periodically removing from the vessel solidified water.

2. The method of claim 1 in which the combustible material is a gas andit is burned with air.

3. The method of claim 1 in which the combustible material is naturalgas and it is burned with air, and the liquefied gas is natural gas.

4. The method of claim 1 in which the combustible material is petroleumgas and it is burned with air, and the liquefied gas is petroleum gas.

5. The method of claim 1 in which the hot products of combustion are fedto the liquefied gas by a tube having its mouth below the liquid levelin the vessel, and the vaporized gas product in admixture with theunsolidified combustion products is thereafter conducted around theoutside of the tube to be further warmed and then is conveyed from thevessel.

6. The method of claim l in which at least some solidified productsremoved from the vessel are vaporized and then admixed with theadmixture of vaporized gas product and combustion products.

7. The method of claim 1 in which solidified water is removed from thevessel and sent to a second vessel and warmed there to melt the ice, thewater is drained from the second tank and vapor is removed from thesecond tank and fed to the admixture of vaporized gas product andcombustion products.

2. The method of claim 1 in which the combustible material is a gas andit is burned with air.
 3. The method of claim 1 in which the combustiblematerial is natural gas and it is burned with air, and the liquefied gasis natural gas.
 4. The method of claim 1 in which the combustiblematerial is petroleum gas and it is burned with air, and the liquefiedgas is petroleum gas.
 5. The method of claim 1 in which the hot productsof combustion are fed to the liquefied gas by a tube having its mouthbelow the liquid level in the vessel, and the vaporized gas product inadmixture with the unsolidified combustion products is thereafterconducted around the outside of the tube to be further warmed and thenis conveyed from the vessel.
 6. The method of claim 1 in which at leastsome solidified products removed from the vessel are vaporized and thenadmixed with the admixture of vaporized gas product and combustionproducts.
 7. The method of claim 1 in which solidified water is removedfrom the vessel and sent to a second vessel and warmed there to melt theice, the water is drained from the second tank and vapor is removed fromthe second tank and fed to the admixture of vaporized gas product andcombustion products.